SC20F Exam Review Notes

Dynamics of Ecosystems

• An ecosystem is a community and its a biotic environment.

• The energy in an ecosystem originally comes from the sun.

• Biotic factors are living, while abiotic factors are non-living.

• Consumers are animals that eat plants or other animals.

• Producers convert radiant energy into chemical energy for ecosystems.

• A food chain is a sequence showing the feeding relationships and energy flow between species.

• The trophic level refers to an organism’s position in a food chain.

• Algae are producers.

Arctic Tundra Food Web

• Plants (cotton sedges) are eaten by caribou, voles, lemmings, ground squirrels, jaegers, and grizzly bears.

• Caribou are eaten by wolves and jaegers.

• Voles and lemmings are eaten by wolves, wolverines, jaegers, gulls, weasels, owls, and hawks.

• Ground squirrels are eaten by wolves, wolverines, weasels, owls, hawks, and grizzly bears.

Carbon Cycle

• Plants absorb carbon dioxide from the atmosphere.

• Carbon dioxide (and water) are converted to carbohydrates by photosynthesis.

• Consumers eat plants, absorbing carbohydrates.

• Carbohydrates (and oxygen) are converted to carbon dioxide by cellular respiration.

Nitrogen Cycle

• Plants obtain nitrogen from nitrates, which are converted from atmospheric nitrogen by bacteria in legume nodules.

• Plants absorb nitrates through their roots.

• Over-fertilization can cause excess nitrogen to run off into rivers and lakes, increasing aquatic plant growth and crowding out other organisms.

Biomagnification

• Biomagnification is the increase in the concentration of a pollutant from one link in a food chain to another.

Carrying Capacity

• Carrying capacity is the largest population of a species that an environment can support.

• Materials and energy: Populations are limited by usable energy from the sun and the supply of water, carbon, and other essential materials.

• Food chains: Populations are limited by the amount of available food and the number of predators.

• Competition: Organisms compete for food, water, and space.

• Density: Overpopulation can lead to disease, fighting, and low birth rates, decreasing the population.

• When a population reaches and exceeds carrying capacity, the death rate increases, causing the population to decrease.

Density-Dependent and Density-Independent Factors

• Density-dependent factors increase in significance as a population grows.

• Density-independent factors' effect on population size does not depend on the number of individuals.

Chemistry In Action

• Electron dot diagrams:

  • Sodium (Na)

  • Magnesium (Mg)

  • Fluorine (F)

  • Sulfur (S)

  • Neon (Ne)

  • K^{+}

  • P^{3-}

  • Cl^{-}

• Naming compounds:

  • KCl: potassium chloride

  • CaBr_2: calcium bromide

  • PbO: lead(II) oxide

  • CuCl_2: copper(II) chloride

  • C3H6: tricarbon hexahydride

  • SiO_2: silicon dioxide

• Chemical formulas:

  • Magnesium sulfide: MgS

  • Nitrogen trioxide: NO_3

  • Lead(IV) sulfide: PbS_2

  • Copper(II) oxide: CuO

  • Magnesium nitride: Mg3N2

  • Dicarbon tetrahydride: C2H4

• Balanced chemical equations:

  • 2Na + Cl_2 \rightarrow 2NaCl (synthesis)

  • 2Al + 3CuCl2 \rightarrow 2Cu + 3AlCl3 (single displacement)

  • H2O2 \rightarrow H2 + O2 (decomposition)

  • C3H8 + 5O2 \rightarrow 3CO2 + 4H_2O (combustion)

  • 2NaC2H3O2 + Cu(NO3)2 \rightarrow Cu(C2H3O2)2 + 2NaNO3 (double displacement)

• Properties of acids:

  • Taste sour

  • Corrode metal

• Properties of bases:

  • Taste bitter

  • Feel slippery

• Common household acids:

  • Fruit juices

  • Carbonated beverages

  • Car battery

• Common household bases:

  • Soap

  • Window cleaner

  • Drain cleaner

  • Quinine

• An indicator shows whether a substance is an acid or a base.

• Using litmus paper: If both red and blue litmus papers turn red, the liquid is an acid. If both turn blue, it is a base.

• Reaction products of an acid and a base: a salt and water.

In Motion

• Frank's average speed:
  v = \frac{d}{t} = \frac{120 \text{ m}}{12 \text{ s}} = 10 \text{ m/s}

• Distance traveled in 30 minutes:
  d = v \cdot t = 10 \text{ m/s} \cdot (30 \text{ min} \cdot 60 \text{ s/min}) = 18000 \text{ m}

• Time to run 200 km:
  t = \frac{d}{v} = \frac{200 \text{ km} \cdot 1000 \text{ m/km}}{10 \text{ m/s}} = 20000 \text{ s}

• Fred Flintstone's acceleration:
  a = \frac{v2 - v1}{t} = \frac{15 \text{ m/s} - 2.5 \text{ m/s}}{10 \text{ s}} = 1.25 \text{ m/s}^2

Duck's Motion

• Total distance traveled: 40 + 60 + 100 + 100 + 60 = 360 m

• Displacement: -40 m (40 m west)

• Motion description:

  • 0-20 s: moving forward (east) at a constant velocity

  • 40-50 s: stationary

  • 70-80 s: moving backwards (west) at a constant velocity

• Velocity from 50-60 s:
  v = \frac{\Delta d}{\Delta t} = \frac{-100 \text{ m}}{10 \text{ s}} = -10 \text{ m/s}

Billy the Badger's Motion

• Motion description:

  • 0-30 s: speeding up while traveling forward (north)

  • 30-50 s: moving forward (north) at a constant velocity

  • 50-70 s: slowing down while traveling forward (north)

  • 150-180 s: slowing down while traveling backward (south)

• Acceleration from 120-140 seconds:
  a = \frac{v2 - v1}{t} = \frac{-0.2 \text{ m/s} - (-0.3 \text{ m/s})}{20 \text{ s}} = 0.005 \text{ m/s}^2

Newton’s Laws of Motion

• First Law: An object at rest remains at rest, and an object in motion remains in motion, unless acted upon by an external unbalanced force.

• Second Law: Force is proportional to mass and acceleration.

• Third Law: To every action, there is an equal and opposite reaction. Forces come in pairs.

• Momentum: A property that depends on the mass and the velocity of the object. All moving objects have momentum. The more massive an object, the more momentum. If two objects have the same mass, the faster object has more momentum.

• Stopping distance problem:
  d = \frac{v^2}{2kv}
  v = 100 \frac{km}{h} = 100 \frac{1000m}{3600s} = 27.8 m/s
  d = \frac{(27.8)^2}{(2 * 0.25 *10 )} = 193 m
  The car will stop in time.

Reaction Time & Stopping Distance

• Reaction time changes the amount of time required to stop a vehicle because the car continues to move forward while reacting. Shorter reaction time allows to stop sooner.

• Stopping distance calculation:
  v = 50 km/h = 13.9 m/s
  Reaction Distance: d = v \cdot t = 13.9 \cdot 1.2 = 16.7 m
  Braking Distance: d = \frac{v^2}{2kv} = \frac{(13.9)^2}{(2 * 0.06 * 10)} = 11.6 m
  Total Stopping Distance = 16.7 + 11.6 = 28.3 m

• Safety features on a car reduce injury to the passengers. (any reasonable response based on the information in the notes and handout)

Weather Dynamics

• The most abundant gas in the atmosphere is nitrogen.

• The layer of the atmosphere closest to the earth is the troposphere.

• The hydrosphere is all of the water on the earth.

• Definitions:

  • Ozone layer: A layer near the top of the stratosphere containing a high concentration of ozone.

  • High pressure system: Air is pushing down.

  • Low pressure system: Air is rising up.

  • Coriolis effect: The apparent bending of the motion of the wind due to the rotation of the earth.

  • Albedo: The ratio of sunlight reflected to the amount of sunlight absorbed.

  • Jet stream: Fast-moving wind in the upper atmosphere that forms between areas of warm and cooler air; they steer storms.

  • Prevailing winds: The direction the wind tends to blow in an area (in Winnipeg, the prevailing winds are from the west).

  • Fujita scale: Scale used to measure the strength of a tornado.

• During El Niño, Winnipeg would experience warmer than normal winter weather.

• Thunderstorm formation: Warm moist air rises, clouds form as warm air carrying moisture rises within cooler air, as the warm air rises, it cools, the moist water vapor begins to condense, as the moisture condenses, energy is released keeping the air warmer than its surroundings, so that it continues to rise, if enough instability is present, the process will continue long enough until cumulonimbus clouds form.

• Staying safe in a thunderstorm: Seek shelter in an enclosed building or car; if outside, lie flat in a forest, crouch down by small low lying bushes.

• Tornado formation: The air in the updraft of a thunderstorm starts to spin, small cyclones of air in the updraft intensify, the air pressure in the center of the cyclone is lower causing it to spin faster and narrower, a funnel cloud appears.

• What to do in a tornado: Go to the basement, go to a designated tornado shelter, stay away from windows and outside walls.

• Blizzard conditions: Heavy falling or blowing snow, winds exceeding 40 km/h, visibility reduced to less than 400 m for at least 4 hours.